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Quantifying information leakage in process calculi
 Proceedings of ICALP’06. Volume 4052 of Lecture Notes in Computer Science
, 2006
"... Building on simple informationtheoretic concepts, we study two quantitative models of information leakage in the picalculus. The first model presupposes an attacker with an essentially unlimited computational power. The resulting notion of absolute leakage, measured in bits, is in agreement with s ..."
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Building on simple informationtheoretic concepts, we study two quantitative models of information leakage in the picalculus. The first model presupposes an attacker with an essentially unlimited computational power. The resulting notion of absolute leakage, measured in bits, is in agreement with secrecy as defined by Abadi and Gordon: a process has an absolute leakage of zero precisely when it satisfies secrecy. The second model assumes a restricted observation scenario, inspired by the testing equivalence framework, where the attacker can only conduct repeated successorfailure experiments on processes. Moreover, each experiment has a cost in terms of communication effort. The resulting notion of leakage rate, measured in bits per action, is in agreement with the first model: the maximum amount of information that can be extracted by repeated experiments coincides with the absolute leakage A of the process. Moreover, the overall extraction cost is at least A/R, where R is the rate of the process. The compositionality properties of the two models are also investigated.
MinEntropy as a Resource
"... Secrecy is fundamental to computer security, but real systems often cannot avoid leaking some secret information. For this reason, it is useful to model secrecy quantitatively, thinking of it as a “resource ” that may be gradually “consumed ” by a system. In this paper, we explore this intuition thr ..."
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Secrecy is fundamental to computer security, but real systems often cannot avoid leaking some secret information. For this reason, it is useful to model secrecy quantitatively, thinking of it as a “resource ” that may be gradually “consumed ” by a system. In this paper, we explore this intuition through several dynamic and static models of secrecy consumption, ultimately focusing on (average) vulnerability and minentropy leakage as especially useful models of secrecy consumption. We also consider several composition operators that allow smaller systems to be combined into a larger system, and explore the extent to which the secrecy consumption of a combined system is constrained by the secrecy consumption of its constituents.
Time and Probability based Information Flow Analysis
"... Abstract—In multilevel systems it is important to avoid unwanted indirect information flow from higher levels to lower levels, namely the so called covert channels. Initial studies of information flow analysis were performed by abstracting away from time and probability. It is already known that sys ..."
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Abstract—In multilevel systems it is important to avoid unwanted indirect information flow from higher levels to lower levels, namely the so called covert channels. Initial studies of information flow analysis were performed by abstracting away from time and probability. It is already known that systems that are proved to be secure in a possibilistic framework may turn out to be insecure when time or probability are considered. Recently, work has been done in order to consider also aspects either of time or of probability, but not both. In this paper we propose a general framework, based on Probabilistic Timed Automata, where both probabilistic and timing covert channels can be studied. We define a NonInterference security property and a Non Deducibility on Composition security property, which allow expressing information flow in a timed and probabilistic setting. We then compare these properties with analogous ones defined in contexts where either time or probability or neither of them are taken into account. This permits a classification of the properties depending on their discerning power. As an application, we study a system with covert channels that we are able to discover by applying our techniques.